1. Field of the Invention
The invention described herein is related to encoding data streams in a wireless communications network. More specifically, the invention is directed to encoding data in multiple-channel, multiple-frequency communication systems so as to provide maximum diversity in space-frequency or in space-time-frequency.
2. Description of the Prior Art
Multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) communication systems, referred to as MIMO-OFDM have exhibited great potential in broadband communications. By employing multiple transmit and multiple receive antennas, many of the adverse effects typically encountered in wireless transmission may be reduced. OFDM modulation may mitigate frequency selective transmission by establishing a plurality of parallel flat-fading channels, thereby providing high spectral efficiency and eliminating the need for complex equalization technology.
Two MIMO-OFDM coding techniques are prevalent in the current art: space-frequency (SF) coding within an OFDM block exploits spatial and frequency diversities, and space-time-frequency (STF) coding, where coding is applied over multiple OFDM blocks to additionally exploit temporal diversities.
Previous SF coding systems have fallen short of achieving full diversity in both space and frequency, usually achieving full diversity in one realm at the expense of full diversity in the other. The same is true for STF codes—full diversity across all three of space, time and frequency has proven elusive. Thus, there is an apparent need for SF and STF coding which can guarantee full-diversity concurrently across all applicable domains.